In communication systems comprising an information transmission link between an information source and an information sink, transmitting and receiving devices are used for information processing and transmission, in which devices
1) the information processing and information transmission can take place in a preferred direction of transmission (simplex mode) or in both directions of transmission (duplex mode),
2) the information processing is analog or digital,
3) the information transmission over the long-distance transmission link is wire-connected or takes place wirelessly on the basis of various FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and/or CDMA (Code Division Multiple Access) information transmission methodsxe2x80x94e.g. according to radio standards such as DECT, GSM, WACS or PACS, IS-54, PHS, PDC etc. [Compare IEEE Communications Magazine, January 1995, pages 50 to 57; D. D. Falconer et al.: xe2x80x9cTime Division Multiple Access Methods for Wireless Personal Communicationsxe2x80x9d].
xe2x80x9cInformationxe2x80x9d is a generic term which stands both for the intelligence (information) and for the physical representation (signal). Even if an information contains the same intelligencexe2x80x94i.e. has the same information contentxe2x80x94different signal forms can occur. Thus, an information relating to an object, e.g., can be transmitted
(1) in the form of an image,
(2) as a spoken word,
(3) as a written word,
(4) as a coded word or image.
In this connection, the type of transmission according to (1) . . . (3) is normally characterized by continuous (analog) signals whilst discontinuous signals (e.g. pulses, digital signals) are usually produced in the case of the type of transmission according to (4).
Based on this general definition of a communication system, the invention relates to a method for controlling the changing of telecommunication channels of a telecommunication subsystem tied into a telecommunication system as local information transmission loopxe2x80x94particularly of a DECTxe2x80x94specific RLL/WLL subsystem (Radio Local Loop) Wireless Local Loop) tied into an ISDN systemxe2x80x94according to the precharacterizing clause of claim 1.
FIG. 1 shows on the basis of the printed documents xe2x80x9cNachrichtentechnik Elektronik, Berlin 45 (1995) Vol. 1, pages 21 to 23 and Vol. 3 pages 29 and 30xe2x80x9d and IEE Colloquium 1993, 173; (1993), pages 29/1-29/7; W. Hing, F. Halsall: xe2x80x9cCordless access to the ISDN basic rate servicexe2x80x9d on the basis of a DECT/ISDN Intermediate System DIIS according to ETSI Publication prETS 300xxx, Version 1.10, September 1996, an xe2x80x9cISDN-to-DECT-specific RLL/WLLxe2x80x9d telecommunication system IDRW-TS (Integrated Services Digital Network-to-Radio in the Local Loop/Wireless in the Local Loop) with an ISDN telecommunication subsystem I-TTS [compare printed document xe2x80x9cNachrichtentechnik Elektronik, Berlin 41-43, Part: 1 to 10, P1: (1991) Vol. 3, pages 99 to 102; P2: (1991) Vol. 4, pages 138 to 143; P3: (1991) Vol. 5, pages 179 to 182 and Vol. 6, pages 219 to 220; P4: (1991) Vol. 6, pages 220 to 222 and (1992) Vol. 1, pages 19 to 20; P5: (1992) Vol. 2, pages 59 to 62 and (1992) Vol. 3, pages 99 to 102; P6: (1992) Vol. 4, pages 150 to 153; P7: (1992) Vol. 6, pages 238 to 241; P8: (1993) Vol. 1, pages 29 to 33; P9: (1993) Vol. 2, pages 95 to 97 and (1993) Vol. 3, pages 129 to 135; P10: (1993) Vol. 4, pages 187 to 190xe2x80x9d] and a DECT-specific RLL/WLL telecommunication subsystem RW-TTS.
In this arrangement, the DECT/ISDN intermediate system DIIS and, respectively, the RLL/WLL telecommunication subsystem RW-TTS are preferably based on a DECT [Digital Enhanced (previously European) Cordless Telecommunication/GAP system DGS; compare (1): Nachrichtentechnik Elektronik 42 (1992) January/February No. 1, Berlin, DE; U. Pilger xe2x80x9cStruktur des DECT-Standardsxe2x80x9d (Structure of the DECT standard), pages 23 to 29 in conjunction with ETSI Publication ETS 300175-1 . . . 9, October 1992; (2): Telcom Report 16 (1993), No. 1, J. H. Koch: xe2x80x9cDigitaler Komfort fxc3xcr schnurlose Telekommunikationxe2x80x94DECT-Standard erxc3x6ffnet neue Nutzungsgebietexe2x80x9d (Digital comfort for cordless telecommunicationxe2x80x94DECT standard opens up new fields of application), pages 26 and 27; (3): tec 2/93xe2x80x94The technical magazine by Ascom xe2x80x9cWege zur universellen mobilen Telekommunikationxe2x80x9d (Approaches to a universal mobile telecommunication), pages 35 to 42; (4): Philips Telecommunication Review Vol. 49, No. 3, September 1991, R. J. Mulder: xe2x80x9cDECT, a universal cordless access systemxe2x80x9d; (5): WO 93/21719 (FIGS. 1 to 3 and associated description)]. The GAP (Generic Access Profile) standard is a subset of the DECT standard which has the task of ensuring the interoperability of the DECT air interface for telephone applications (compare ETSI Publication prETS 300444 April 1995).
As an alternative, the DECT/ISDN intermediate system DIIS and, respectively the RLL/WLL telecommunication subsystem RW-TTS, can also be based on a GSM system (Groupe Spxc3xa9ciale Mobile or Global System for Mobile Communication; compare Informatik Spektrum 14 (1991) June, No. 3, Berlin, DE; A. Mann: xe2x80x9cDer GSM-Standard-Grundlage fxc3xcr digitale europxc3xa4ische Mobilfunknetzexe2x80x9d (The GSM standardxe2x80x94basis for digital European mobile radio networks), pages 137 to 152). In the context of a hybrid telecommunication system it is also possible, instead, for the ISDN telecommunication subsystem I-TTS to be constructed as GSM system.
In addition, further possibilities to be considered for implementing the DECT/ISDN intermediate system DIIS and, respectively, the RLL/WLL telecommunication subsystem RW-TTS or the ISDN telecommunication subsystem I-TTS are the systems mentioned initially, and future systems which are based on the known multiple-access methods FDMA, TDMA, CDMA (Frequency Division Multiple Access, Time Division Multiple Access, Code Division Multiple Access) and hybrid multiple access methods formed from these.
The use of radio channels (e.g. DECT channels) in traditional line-connected telecommunication systems such as the ISDN is gaining increasing significance, particularly against the background of future alternative network operators without their own complete wire-line network.
Thus, it is intended to provide the ISDN subscriber with ISDN services at standard ISDN interfaces by means of the wireless RLL/WLL (Radio in the Local Loop/Wireless in the Local Loop) line interfacing system, e.g. including the DECT system DS, for example in the RLL/WLL telecommunication subsystem RW-TTS (compare FIG. 1).
In the xe2x80x9cISDN-to-DECT-specific RLL/WLLxe2x80x9d telecommunication system IDRW-TS according to FIG. 1, a telecommunication subscriber (user) TCU (Telecommunication User) with his terminal equipment TE (also Terminal Endpoint) is tied, e.g. via a standardized S interface (S-BUS), the preferably DECT-specific DECT/ISDN intermediate system DIIS (first telecommunication subsystem) contained in the RLL/WLL telecommunication subsystem RW-TTS and constructed as local information transmission loop, a further standardized S interface (S-BUS), a network termination NT and a standardized U interface of the ISDN telecommunication subsystem I-TTS (second telecommunication subsystem) into the ISDN world and all the services available therein.
The first telecommunication subsystem DIIS essentially consists of two telecommunication interfaces, a first telecommunication interface DIFS (DECT Intermediate Fixed System) and a second telecommunication interface DIPS (DECT Intermediate Portable System) which are connected to one another wirelessly, e.g. via a DECT air interface. Because of the quasi-stationary first telecommunication interface DIFS, the first telecommunication subsystem DIIS forms the local information transmission loop defined above in this connection. The first telecommunication interface DIFS contains a radio fixed part RFP, an interworking unit IWU1 and an interface circuit INC1 to the S interface. The second telecommunication interface DIPS contains a radio portable part RPP and an interworking unit IWU2 and an interface circuit INC2 to the S interface. In this arrangement, the radio fixed part RFP and the radio portable part RPP form the familiar DECT/GAP system DGS.
To have a DECT-specific RLL system as bearer for all ISDN services, if possible, in the subscriber loop, the following general problems arise:
a) formulation of the ISDN channel structure (D channel and 2 B channels), especially of the D channel in the text which follows,
b) good economy of bandwidths; particularly significant for ISDN since some services already need two DECT channels for the B channel data rate of 64 kb/s,
c) minimum technical complexity.
Simulation of the D Channel
Properties of the D Channel
Common signalling channel on the C plane for all terminal endpoints TE connected to the ISDN line.
The TE-specific signalling channels to the network are separated there by TE-individual addresses TEI (Terminal Endpoint. Identifiers). The order of information is in short TE-individually by the access mechanism to the D channel.
Throughput: 16 kb/s
Usage: depends on many criteria, as a rule lower than maximum capacity; congestion situations are possible but can be, rapidly cleared because of the high capacity.
DECT Channels
FIG. 2 shows the TDMA structure of the DECT/GAP system TKS in accordance with the printed document xe2x80x9cNachrichtentechnik Elektronik 42 (1992) January/February, No. 1, Berlin, DE; U. Pilger: xe2x80x9cStruktur des DECT-Standardsxe2x80x9d (Structure of the DECT standard), pages 23 to 29 in conjunction with ETS 300 175-1 . . . 9, October 1992xe2x80x9d. With respect to the multiple access methods, the DECT/GAP system is a hybrid system in which radio messages can be sent on ten frequencies in the frequency band between 1.88 and 1.90 GHz according to the FDMA principle within a predetermined time sequence according to the TDMA principle according to FIG. 2 from the base station RFP to the mobile part RPP and from the mobile part RPP to the base station RFP (duplex mode). The time sequence is determined by a multi-timeframe MZR which occurs every 160 ms and which has 16 timeframes ZR having in each case a duration of 10 ms. Within these time frames ZR, information relating to a C, M, N, P, Q channel defined in the DECT standard is transmitted separately to the base station RFP and the mobile part RPP. Thus if information for several of these channels is transmitted within one timeframe, the transmission takes place in accordance with a list of priorities, where M greater than C greater than N and P greater than N. Each of the 16 timeframes ZR of the multi-timeframe MZR is, in turn, subdivided into 24 time slots ZS having in each case a duration of 417 xcexcs, of which 12 time slots ZS (time slots 0 . . . 11) are intended for the xe2x80x9cbase station RFPxe2x86x92mobile part RPPxe2x80x9d direction of transmission and a further 12 time slots ZS (time slots 12 . . . 23) are intended for the xe2x80x9cmobile part RPPxe2x86x92base station RFPxe2x80x9d direction of transmission. In each of these time slots ZS, information having a bit length of 480 bits are transmitted in accordance with the DECT standard. Of these 480 bits, 32 bits are transmitted as synchronization information in a SYNC field and 388 bits are transmitted as user information in a D field. The remaining 60 bits are transmitted as additional information in a Z field and as guard information in a xe2x80x9cguard timexe2x80x9d field. The 388 bits of the D field, transmitted as user information, are, in turn, subdivided into a 64-bit-long A field, a 320-bit-long B field and a 4-bit-long xe2x80x9cX-CRCxe2x80x9d word. The 64-bit-long A field is composed of a header with a length of 8 bits, a data record with data for the C, Q, M, N, P channels with a length of 40 bits and an xe2x80x9cA-CRCxe2x80x9d word with a length of 16 bits.
Properites
Use of TDMA time slots.
In principle, one Cs channel (s=slow) is used for signalling [C plane in the DECT standard] and an associated channel is used for the user information [U Plane in the DECT standard] (32 kb/s throughput).
Throughput of the Cs channel: 2 kb/s.
The DECT standard also offers other channel structures, e.g. a Cf channel (f=fast).
The Cf channel occupies one time slot.
Throughput of the Cf channel: 25.6 kb/s.
Based on the OSI/ISO reference model [compare (1): Unterrichtsblxc3xa4tter (Training sheets) Deutsche Telecom Vol. 48, 2/1995, pages 102 to 111; (2): ETSI Publication ETS 300175xe2x80x941 . . . 9, October 1992; (3): ETSI Publication ETS 300102, February 1992; (4): ETSI Publication ETS 300125, September 1991; (5): ETSI Publication ETS 300012, April 1992], FIG. 3 shows a model of the C plane of the xe2x80x9cISDN-to-DECT-specific RLL/WLLxe2x80x9d telecommunication system IDRW-TS according to FIG. 1.
Based on the OSI/ISO reference model [compare (1): Unterrichtsblxc3xa4tter (Training sheets) Deutsche Telecom Vol. 48, February/1995, pages 102 to 111; (2): ETSI Publication ETS 300175xe2x80x941 . . . 9, October 1992; (3): ETSI Publication ETS 300102, February 1992; (4): ETSI Publication ETS 300125, September 1991; (5): ETSI Publication ETS 300012, April 1992], FIG. 4 shows a model of the U plane for voice data transmission of the xe2x80x9cISDN-to-DECT-specific RLL/WLLxe2x80x9d telecommunication system IDRW-TS according to FIG. 1.
Economy of Bandwidths
The Cs channel structure offers optimum economy of bandwidths for a standard voice connection since, according to FIG. 5, on the basis of FIGS. 3 and 4 and taking into consideration the ETSI Publications (ETS 300175-1, October/1992, Section 7; ETS 300175-3, October/1992, Section 4.1; ETS 300175-4 10/1992, Section 4), only one transmission path (bearer)xe2x80x94e.g. MBC with the LCNy, LCN1 according to FIG. 5xe2x80x94or, respectively, one connection or one time slot is needed.
According to FIG. 5 and on the basis of FIGS. 3 and 4 and taking into consideration the ETSI Publications (ETS 300175-1, October/1992, Section 7; ETS 300175-3, October/1992, Section 4.1; ETS 300175-4 October/1992, Section 4), the use of the Cf channel leads to less economy of bandwidths since the U plane itself needs a further transmission path (bearer) or, respectively, a further connection or a further time slot; i.e. two bearersxe2x80x94e.g. MBC with the LCN2, LCNz and MBC with the LCNy, LCN1 according to FIG. 5xe2x80x94or, respectively, two connections or two time slots are needed for a simple voice connection.
Moreover, three bearersxe2x80x94e.g. MBC with the LCNx, LCN0, MBC with the LCNy, LCN1 and MBC with the LCNz, LCN2 according to FIG. 5xe2x80x94or, respectively, three connections or three time slots are required where there are two ISDN B channel connections (voice connections).
Although it appears to be appropriate to use the Cf channel from the point of view of channel capacity, the use of the Cs channel is appropriate from the point of view of economy of bandwidths.
Independently of whether it is the Cf channel or the Cs channel which is used for setting up the connection (setting up bearers), it must be ensured (compare FIG. 5), that it is possible to change from Cf channel to the Cs channel and conversely at any time (changing channels between channels of unequal channel capacity). In addition, it must be ensured that it is possible to change between a first Cs channel and a second Cs channel (changing channels between two channels of equal channel capacity) because of the possibility that the two connections (bearers) can be set up at the same time in the ISDN system (2 B channels).
The object forming the basis of the invention consists in controlling in a simple manner changes from information usually transmitted in the telecommunication subsystem, in a telecommunication subsystem which is tied into a telecommunication system as local information transmission loopsxe2x80x94especially a DECT-specific RLL/WLL subsystem tied into an ISDN system.
Proceeding from controlling the change of channel in a telecommunication subsystem which is tied into a telecommunication system as local information transmission loopxe2x80x94especially a DECT-specific RLL/WLL subsystem tied into an ISDN systemxe2x80x94mentioned and outlined initially, by means of two commands, one first command designed as switch-over command and a second command designed as switch-over response, the idea underlying the invention is as follows:
to designationally initiate the channel change;
to provide a time control in conformity with which a further switch-over command is transmitted given failure of the switch-over response to arrive in response to the switch-over command;
the switch-over response confirms that the switching has already been underaken;
to initiate and implement the channel change by means of a time-limited interruption of the information or, respectively, message transmission in the telecommunication system and subsequent resumption of the information, or respectively, message transmission;
for a change of channel from a DECT-specific Cf channel to a DECT-specifice Cs channel, this is preferably done, by means of an ATTRIBUTE_REQUEST information element tied into the DECT protocol as switch-over command and an ATTRIBUTE_CONFIRM information element tied into the DECT protocol as switch-over response or, respectively, by means of a SUSPEND information element tied into the DECT protocol as switch-over command and a RESUME information element tied into the DECT protocol as switch-over response); and
before the transmission of the system information, subsystem-specific parameters prescribed on the other subsystem channel are reset;
after the channel change, a test message with request for acknowledgment is sent;
the information is transmitted according to a predetermined transmission principle with a predetermined transmission sequence and, after a channel change, is transmitted on the other subsystem channel with an optimally small transmission sequence;
system message with payload information and/or the system information and/or the subsystem information are transmitted between the telecommunication interfaces of the telecommunication subsystem on transmission paths with different identifiers.